In video applications there may be a large number of video and/or graphic display formats that may be supported by many different vendors. These different video display formats may differ, at least in part, in their horizontal resolution, vertical resolution, and/or aspect ratio, for example. The selection of a particular video display format may depend on user and/or vendor specification. The use of a particular video display format may also be determined by standard specifications, for example. In order to enable system components that support one type of video display format to operate with system components that support a different type of video display format, video systems may utilize video or graphic scalers. Video scalers may be adapted to provide down scaling and/or up scaling operations.
A polyphase filter (PPF) may be utilized to perform filtering operations when implementing video and graphic scalers in video systems. Usually, a sub-filter with phase that is closest to the desired output sample is utilized to generate the output sample as an approximation. In order to mitigate approximation errors, the number of phases of the polyphase filter may need to be sufficiently large, generally resulting in an increase in system cost. Another approach may be to interpolate between two sub-phase filters in order to alleviate the phase accuracy limit of a PPF with a small number of phases such as 4 or 8 phases, for example. However, usually even with such an approach, the number of required multiplications may still be large, resulting in no effective reduction in system cost. Therefore, these kinds of algorithms and/or architectures, when utilized in video scalers, may still get quite large and may result in the use of a considerable amount of gates in silicon. Simplified methods of resolving this problem generally suffer from loss of scaling quality. Often, the resulting phase noise is visible and undesirable. Additionally, the size reduction that may be achieved is often not significant compared to the resultant undesirable effects.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.